Electrical switch with interlocking mechanism



March 1956 T. J. RYS ETAL ELECTRICAL SWITCH WITH INTERLOCKING MECHANISM 7 Sheets-Sheet l E I jar 2 46f jl'dr zfiacl Filed Dec. 5, 1962 March 15, 1966 T J, RYS ETAL 3,240,888

ELECTRICAL SWITCH WITH INTERLOCKING MECHANISM Filed Dec. 5, 1962 7 Sheets-Sheet 2 INVENTORS I KGDMQJQM aw March 15, 1966 T. J. RYS ETAL 3,240,888

ELECTRICAL SWITCH WITH INTERLOCKING MECHANISM Filed Dec. 5, 1962 7 Sheets-Sheet 5 INVEMORI Jidzwz JJZ 5 March 15, 1966 J s ETAL 3,240,883

ELECTRICAL SWITCH WITH INTERLOGKING- MECHANISM '7 Sheets-Sheet 4 Filed Dec. 5, 1962 INVENTORS J z (Zip; yflar'miijlfiwzba March 15, 1966 T. J. RYS ETAL ELECTRICAL SWITCH WITH INTERLOCKING MECHANISM 'T Sheets-Sheet 5 Filed Dec. 5, 1962 INVENTOR5 March 15, 1966 T. J. RYS ETAL ELECTRICAL SWITCH WITH INTERLOCKING MECHANISM T Sheets-Sheet 6 Filed Dec. 5, 1962 Z IN VENTORS March 15, 1966 s T 3,240,888

ELECTRICAL SWITCH WITH INTERLOCKING MECHANISM Filed Dec. 5, 1962 7 Sheets-Sheet 7 i jgm,

4'? J00 INVENTORS United States Patent 3,240,888 ELECTRICAL SWITCH WITH INTERLOCKING MECHANISM Tadensz .I. Rys and Harris I. Stanback, Lexington, Ky.,

assignors to Square D Company, Park Ridge, 11]., a

corporation of Michigan Filed Dec. 5, 1962, Ser. No. 242,423 7 Claims. (Cl. 20050) This invention relates generally to electrical switches, and more particularly to enclosed or safety switches.

An object of the invention is to provide an improved safety switch.

Another object is to provide an improved safety switch of the single throw, single make and break type.

A further object is to provide an improved multipole safety switch.

Yet another object is to provide an improved multipole safety switch in which a pivotally mounted blade carrier carries a plurality of pivotally mounted blades respectively adapted to engage a plurality of stationary contacts and also carries a corresponding plurality of biasing springs, each biasing spring being operatively associated with one of the blades intermediately of the ends of the blade to retain one end portion of the blade in its pivotal mounting and to establish pressure between the other end portion of the blade and its respective stationary contact when the blade and contact are engaged, and the biasing springs also being operatively associated with the blade carrier to aid in retaining the blade carrier in its pivotal mounting.

Still another object is to provide an improved multipole safety switch of the fusible type.

A still further object is to provide an improved multipole fusible safety switch including a base, a plurality of pairs of axially aligned fuse holders mounted on the base, a plurality of stationary contact members mounted on the base and respectively spaced generally axially from the pairs of fuse holders, a blade carrier pivotally mounted on the base, a plurality of switch blades carried by the blade carrier and having first end portions respectively engageable with the stationary contact members and second end portions respectively pivotally mounted on the fuse holders of each pair closer to the stationary contact members, and a plurality of biasing springs carried by the blade carrier and respectively operatively associated with the switch blades between the end portions thereof to establish pressure between the first end portions thereof and the stationary contact members when the first end portions of the switch blades are in engagement with the stationary contact members and to retain the second end portions of the switch blades in pivotal engagement with the fuse holders of each pair closer to the stationary contact members, the biasing springs also being operatively associated with the blade carrier to aid in retaining the blade carrier in pivotal engagement with the base.

Another object is to provide an improved multipole fusible safety switch in which a minimum number of electrical joints is provided between the fuse holder of each fusible pole and the corresponding electrical connector for a power supply line.

Still another object is to provide a safety switch having an improved arrangement for a spring latch which forms a part of an interlock means for the cover and the switch operating handle.

A still further object is to provide a safety switch having an improved quick-make, quick-break operating mechanism including an operating cam operatively associated with a pivotally mounted movable contact blade carrier and forming a part of a defeatable interlock means for an "ice operating handle and cover which normally prevents opening of the cover when the switch is in on position.

Yet another object is to provide a multipole safety switch having an operating handle pivotally mounted on a pin forming a part of a defeatable interlock means for an operating handle and cover, the pin having an operating cam fixed on an inner end thereof and operatively associated with a pivotally mounted contact blade carrier and cooperable with a spring latch for the cover to normally prevent opening thereof when the switch is in on position.

Other objects and advantages will appear when the following specification is considered along with the accompanying drawings in which:

FIGURE 1 is a front elevational view of a fusible safety switch constructed in accordance with the invention;

FIGURE 2 is a side elevational view of the switch of FIGURE 1;

FIGURE 3 is a top view of the switch of FIGURE 1;

FIGURE 4 is a fragmentary perspective view of the switch of FIGURE 1 showing particularly the latch for the front cover;

FIGURE 5 is a front elevational view of the switch of FIGURE 1 with the cover and certain other portions removed, and certain other parts broken away or in section, the switch blades being shown in on position;

FIGURE 6 is a view taken substantially along section line 6-6 of FIGURE 5;

FIGURE 7 is a view taken substantially along section line 77 of FIGURE 5;

FIGURE 7a is a fragmentary sectional view showing a modified form of the fuse clips of FIGURE 7;

FIGURE 8 is a view taken substantially along section line 88 of FIGURE 5;

FIGURE 9 is a view taken substantially along section line 99 of FIGURE 5 but showing the switch blades in off position;

FIGURE 10 is a perspective view of the blade carrier of the switch of FIGURE 1;

FIGURE 11 is a sectional view taken substantially along the line 1111 of FIGURE 10;

FIGURE 12 is a sectional view of the blade carrier of FIGURE 10 taken substantially as indicated by line 1212 of FIGURE 11;

FIGURE 13 is a sectional view of the blade carrier of FIGURE 10 taken substantially as indicated by line 1313 of FIGURE 11;

FIGURE 14 is a perspective view of one of the arc shields of the switch of FIGURE 1;

FIGURE 15 is a fragmentary view similar to FIGURE 2 but with portions of the box and cover broken away, the operating mechanism of the switch being shown in on position;

FIGURE 16 is a fragmentary front elevational view of the operating mechanism of the switch, portions of the cover and the latch therefor being broken away;

FIGURE 17 is a view of portions of the operating mechanism shown in FIGURE 15, but illustrating a different position thereof for defeating the switch and cover interlock means;

FIGURE 18 is a view taken substantially along section line 18-18 of FIGURE 16, but showing the operating mechanism of the switch in off position;

FIGURE 19 is a view taken substantially along section line 1919 of FIGURE 18;

FIGURE 20 is a perspective view of the operating cam of the switch operating mechanism; and

FIGURE 21 is a fragmentary perspective view of a portion of the handle of the switch operating mechanism.

With reference to the drawings, and particularly to FIGURES 1-4, a fusible safety switch 30 constructed in accordance with the invention includes an open-front metal box 32 closable by a cover 34 hinged to the lefthand side thereof as viewed in FIGURE 1. An operating handle 36 for the switch is mounted for pivotal movement between on and off positions on a pin 38 which has a slotted head, and, as hereinafter described, forms part of a defeatable interlock means for the switch operating handle 36 and the cover 34. For compactness and to permit mounting of a plurality of switches 30 in closely spaced side-by-side relationship, the operating handle 36 is formed and arranged to be generally within the broad outline of the box 32 and cover 34. The cover 34 is provided with flange portions which overlap the front edges of the box 32, but is cut away adjacent the handle 36 and is provided with an aperture 40 for the reception of an car 42, to be hereinafter more fully described, having a hole 43 therein for the reception of a padlock hasp to lock the cover 34 closed. A latch member 44, also to be more fully described hereinafter, is provided for latching cover 34 closed when a padlock is not used in the ear 42. The latch member 44 has a tongue 45 engageable with the outside of the cover 34 to retain it in closed position. The tongue 45 normally prevents opening and closing of the cover 34 when the handle 36 is in on position; but when the handle 36 is in off position, and also when the defeata'ble interlock means is operated by the turning of the pin 38 with a screwdriver when the handle 36 is in on position, the outer end of the latch member 44 may be resiliently deformed as more fully described hereinafter to release the cover 34 from the tongue 45.

A hole 46 is provided in a handle 36 and a hole 48 is provided in the latch member 44, a padlock hasp inserted in either of the holes 46 and 48 serving to prevent opera; tion of the handle 36 from one extreme position to the other and thus effectively locking the switch blades, to be later described, in open or closed position.

In FIGURES -9, a molded insulating base 50 is shown secured to the back of the box 32 in any suitable manner. The fastening means shown includes a pair of screws 51 (FIGURES 5 and 9) threaded into the back of the box and a hook 52 formed on the back of the box and adapted to be received in a recess 53 to retain the base. The base 50 serves as a mounting for a four-pole solid-neutral switch including three fusible poles having cooperable contacts and one solid-neutral pole. The solid-neutral pole includes a solid-neutral strap 55, an electrical connector 56 for the neutral wire of a four-wire, three-phase source of electrical power, an electrical connector 57 for the neutral wire of a four-wire three-phase load, and an electrical connector 58 for the connection to ground. A single screw 60 secures the strap 55 and the connector 58 to the base, and the connectors 56 and 57 are held in suitable recesses in the base by opposite ends of the strap 55. For three-wire ungrounded systems, the solid-neutral strap 55 and its associated connectors may be eliminated.

Each of the three fusible poles includes an upper and a lower composite fuse holder, the upper one having a switch blade pivotally mounted thereon and the lower one having a load terminal associated therewith. Further, each composite fuse holder includes a relatively rigid conductive portion and a resilient clamping portion. Thus, as shown best in FIGURE 7, upper fuse holders including relatively rigid conductive portions 62a, 62b, and 62c and resilient clamping portions 63a, 63b, and 630 are secured to the base 50 by means of screws 64a, 64b, and 64c which are threaded into the relatively rigid portions 62a, 62b, and 620, respectively. The resilient clamping portions and the relatively rigid portions are substantially L-shaped, but the relatively rigid portions are curved to form pockets for ferrules of cartridge fuses and are additionally provided with holes forming pivotal bearing surfaces for switch blades 66a, 66b, and 660, respectively, which have protuberances 65a, 65b, and 650 projecting into the bearing holes.

In FIGURE 7a, a modified form of the resilient clamping portion of a composite fuse holder is shown. Thus, if desired, the L-shaped resilient clamping portions 63a, 63b, and 63c may be replaced by resilient clamping portions such as a generally U-shaped clamping portion 63g, which is similar to the L-shaped clamping portions 63a, 63b, and 630, but has an additional leg extending over a switch blade 66g to aid in retaining a protuberance 65g thereof in a bearing hole in a relatively rigid conductive portion 62g of a composite fuse holder.

As shown in FIGURES 5, 8, and 9, the lower fuse holders including resilient clamping portions 63d, 63c, and 63 and relatively rigid conductive portions 68a, 68b, and 680 are secured to the base 50 by means of screws 64d, 64c, and 64 which are threaded into the relatively rigid portions 68a, 68b, and 68c, respectively. The relatively rigid portions 68a, 68b, and 68c of the lower fuse holders differ from the relatively rigid portions 62a, 62b, and 620 of the upper fuse holders in that they do not have switch blades associated therewith, and they are provided with extensions parallel to the base 50 for securing electrical connectors 57a, 57b, and 57c respectively thereto, as best shown in FIGURE 8. The electrical connectors 57a, 57b, and 570 respectively form the load terminals of the three fusible poles.

Electrical connectors 56a, 56b, and 560 forming the line terminals of the three fusible poles are secured to the base 50 by extensions of generally L-shaped stationary contact members 70a, 70b, and 700, respectively, which in turn are secured to the base 50 :by means of screws 64g, 64h, and 641'. The line terminals or electrical connectors 56, 56a, 56b, and 560 and the load terminals or connectors 57, 57a, 57b, and 57c are preferably of the type shown and described in copending application, Serial No. 106,106, filed on April 27, 1961, now Patent No. 3,133,781, issued May 19, 1964, and assigned to the assignee of the present invention. The contact areas of the upstanding leg portions of the generally L-shaped stationary contact members 70a, 70b, and 700 engageable by the switch blades 66a, 66b, and 66c are shielded from the line terminals 56a, 56b, and 56c by insulating members 72a, 72b, and 72c respectively, which are identical to insulating member 72 shown in FIGURE 14, a small apertured portion 73 of each insulating member being secured between the base 50 and a leg portion of a stationary contact member 70 extending parallel to the base 50.

The switch blades 66a, 66b, and 66c, while being pivotally mounted on the relatively rigid portions 62a, 62b, and 620, respectively, of the upper fuse holders, are also mounted in a molded insulating blade actuator or carrier 76 forming an important part of this invention. The blade carrier 76 is formed with appropriate slots for respectively receiving the switch blades, as can best be seen in FIGURES 11-13, and also with appropriate pockets for respectively receiving compression springs 78a, 78b, and 78c, the spring pockets intercepting the blade slots so that one end of each spring is seated on a blade. The blade carrier 76 is pivotally mounted on the base 50, and more specifically on a pair of upstanding post portions 80 and 81 having recesses or slots 82 and 83 in respective corresponding sides thereof. The carrier is provided with recesses 86 and 87 for laterally receiving post portions 80 and 81, respectively, and with cylindrieal projections 88 and 89 which are adapted to be laterally received in the recesses or slots 82 and 83, respectively. The arrangement may be visualized best from FIGURE 10 in which the 'post portions 80 and 81 are shown in phantom. In assembling, the carrier without switch blades is placed on the post portions but offset from its final assembled position thereon so that the projections 88 and 89 will clear the post portions.

Thereafter, the carrier is shifted laterally of the post portions to place the projections 88 and 89, respectively, in the slots 82 and 83, and engagement of the projections with the closed ends of the slots then prevents removal of the carrier directly axially of the post portions. The switch blades 66a, 66b, and 660 are then inserted in the blade carrier and projecting portions 65a, 65b, and 650 inserted in the bearing holes of the rigid portions 62a, 62b, and 620 of the upper fuse clips, the switch blades and associated springs 78a, 78b, and 78c then preventing shifting of the carrier back laterally of the post portions and thus maintaining the projections 88 and 89 in the slots 82 and 83.

The base 50 is provided with a slot 92 (FIGURE 9) through which a projection 93 on the blade carrier 76 extends to limit pivotal movement of the carrier in a switch opening direction by engagement with the base 50 at the end of the slot, as shown in FIGURE 9.

- A lug 95 is provided on one end of the blade carrier 76 for cooperation with an operating cam 96 shown in FIGURES 20, the cam being best shown in FIGURE and the cooperative relationship between the lug 95 and the cam being illustrated in FIGURES 15, 16, and 18. The cam 96 is provided with a hole 97 (FIGURE 20) for receiving the inner end of the pin 38 on which it is fixedly mounted for rotation therewith as a unit. The pin 38 is supported by bearing holes formed in an outwardly offset portion 99 of the right-hand side of the box 32 and in a formed plate 100 which overlaps the offset portion 99 and is riveted to the inside of the righthand side of the box by a pair of rivets 101a and 101b. The car 42 previously described is an integral part of the'plate 100.

The handle 36 is pivotally mounted on the pin 38 between offset portion 99 of the box and plate 100, a hole 103 (FIGURE 21) being provided for this purpose, and an inwardly projecting lug 104 is provided radially of the hole 103 on the flat inner end of the handle, the plate 100 having an arcuate slot 106 through which the lug 104 projects into a slot 108 in the cam 96.

A quick-make and quick-break action between the switch blades 66a, 66b, and 660 and the stationary contact members 70a, 70b, and 700, respectively, is provided by an over-center compression spring 110 operatively connected to the cam 96. The spring 110 is retained on an actuator 112 which extends therethrough and is reciprocally mounted in a bracket 113 formed integrally with the plate 100, the spring being compressed between the bracket 113' and a shouldered portion 1 14. on the actuator. The actuator 112 includes a pin 116 having an enlarged head portion, the pin 116 being received in a generally T-shaped slot 117 formed in the carn 96.

The cam 96 is provided with a pair of inwardly oifset blade carrier actuating portions 120 and 121 having respective cam surfaces 122 and 123 alternatively engageable with the lug 95 on opposite sides thereof. The pivotal movement of the cam 96 in opposite directions is limited by a stop engaging projection 124 thereon having a surface 125 engageable with a flange 128 on the formed plate 100 and a surface 126 engageable with a stop 129 formed on the plate 100. A locking tongue 130 on the cam 96 is cooperable with a tongue 132 formed on the latch member 44, as best shown in FIG- URE 15. The latch member 44 is pivotally mounted on the pin 38 but is prevented from rotating by engagement of the tongue 132 in a notch 133 (FIGURE 18) provided in the plate 100. I I

When the switch is in on position, the locking tongue 130 is normally aligned with the tongue 132 and substantially prevents bending of the outer end of the latch member 44, and the tongue 45 on the latch member interferes with opening and closing of the cover 34. Further, this interlock may not be defeated by merely moving the handle 36 part way toward off position of the switch without disengaging the blades 66a, 66b, and 660 from the stationary contact members 70a, 70b, and 700, for when the handle 36 is moved far enough for the lug 104 thereon to rotate the locking tongue 130 out of alignment with the tongue 132, the handle 36 itself then prevents bending of the outer end of the latch member 44 and maintains the tongue 45 in interfering relationship with the cover 34. However, the interlock can be defeated by turning the pin 38 sufficiently to rotate the locking tongue 130 out of alignment with the tongue 132, as shown in FIGURE 17, thus allowing the outer end portion of the latch member 44 to be bent sufiiciently to move the tongue 45 out of interfering relationship with the cover 34 so that the cover can be opened by authorized persons while the switch is in on position. It is unlikely that unauthorized persons will know that the pin 38 may be turned to defeat the interlock.

A torsion spring 134 is provided to bias the handle 36 toward its extreme positions. One end of the spring 134 is anchored in a bracket portion 135 of the formed plate and the other end is connected to the handle 36. The spring is pre-stressed so that it tends to unwind. Thus, in FIGURE 15, the spring tends to rotate the handle 36 clockwise toward off position, and in FIGURE 18, where it is viewed from the opposite side, the spring tends to rotate the handle 36 clockwise toward on" position.

The slot 108 in the cam 96 has a longer arcuate length than the lug 104 on the handle 36 to provide a lostmotion connection enabling the over-center spring to operate the cam 96 with a snap action without any restraint by the handle once the line of action of the spring has shifted across the pivotal axis of the cam. The snap movement of the cam is enhanced by the lostmotion connection between the pin 116 and the generally T-shaped slot 117, a shifting of the pin across the head of the T having an impact effect on the cam as the line of action of the spring 110 is shifted across the pivotal axis of the cam. Further, the cam surfaces 122 and 123'are spaced farther apart than the width of the lug 95 on the blade carrier 76 to provide a lost-motion connection enabling the cam to enter its snap movement before suflicient opening movement of the blade carrier 76 occurs to cause disengagement of the switch blades 66a, 66b, and 660 from the stationary contact member-s 70a, 70b, and 700.

The lost-motion connections between the handle 36 and cam 96 and between the cam 96 and blade carrier 76 also enable the cam 96 to be turned by the screw 38 to defeat the interlock between the cover 34 and handle 36.

Various modifications may be made in the structure disclosed without departing from the spirit and scope of the invention.

We claim:

1. A safety switch comprising an open-front box having a rear wall and a pair of opposed first and second side walls, an openable cover pivotally mounted on said firstvside wall and normally closing the open front of said box, a stationary contact member mounted in said box, a blade actuator movably mounted in said box, a switch blade mounted in said box and movable by said blade actuator between an open position in which it is electrically disconnected from said stationary contact member and a closed position in which it is electrically connected to said stationary contact member, an operating handle pivotally mounted on said second side wall for movement between OFF and ON positions corresponding respectively to said open and closed positions of said switch blade, a releasable latch member mounted on said second side wall and disposed between said handle and said first side wall, said latch member projecting for wardly beyond a front surface of said cover when said cover is in closed position and having a latching portion normally overlapping said front surface of said cover to latch said cover in closed position, the outer end portion of said latch member being movable in a direction away from said first side wall when said handle is in said OFF position and said switch blade is in said open position to move said latching portion out of latching relationship with said cover, an operating cam pivotally mounted on said second side wall, first lost motion connection means operatively connecting said handle and cam, second lost motion connection means operatively connecting said cam and blade actuator, a pair of spaced stop means in said box respectively engageable by said cam and respectively limiting pivotal movement thereof in opposite directions, an over-center cam-biasing spring, and means operatively connecting said cam-biasing spring and said cam, said cam-biasing spring selectively biasing said cam in opposite direotions into engagement respectively with said stop means, said cam and latch member having portions which interlock and prevent movement of said outer end portion of said latch member in a direction away from said first side wall and movement of said latching portion out of latching relationship with said cover when said switch blade is in said closed position and said handle is in said ON position and said cam is biased into engagement with the corresponding one of said stop means by said cam-biasing spring, and said cam being pivo-table against the force of said spring out of interlocking relationship with said latch member to a predetermined position between said stop means without shifting the line of action of said cam-biasing spring over the pivotal axis of said cam, thereby to permit said outer end portion of said latch member to be moved in a direction away from said first side wall and said latching portion to be moved out of latching relationship with said cover and said cover to be opened while said switch blade is in said closed position and said handle is in said ON position.

2. A safety switch as claimed in claim 1, wherein when said handle is in said ON position and said switch blade is in said closed position, said handle may be moved to a predetermined intermediate position to move said cam to said predetermined positionthereof between said stop means and out of interlocking relationship with said latch member without shifting the line of action of said cambiasing spring over the pivotal axis of said cam, said handle when in said intermediate position having a portion preventing movement of said outer end portion of said latch member in a direction away from said first side wall and movement of said latching portion out of latching relationship with said cover, whereby said latching portion may be moved out of latching relationship with said cover and said cover may be opened while said switch blade is in said closed position solely by prior pivotal movement of said cam to said predetermined position thereof independently of said handle.

3. A safety switch as claimed in claim 1, including an over-center handle-biasing spring and means operatively connecting said handle-biasing spring to said handle, said handle-biasing spring being movable with said handle to shift the line of action thereof over the pivotal axis of said handle as said handle is moved between said ON and OFF positions, whereby said handle-biasing spring selectively biases said handle in opposite directions.

4. A safety switch as claimed in claim 1, wherein said operating handle is positioned on the side of said second side wall closer to said first side wall.

5. A safety switch comprising an open-front box having a rear wall and a pair of opposed first and second side walls, an openable cover pivotally mounted on said first side wall and normally closing the open front of said box, a. stationary contact member mounted in said box, a blade actuator pivotally mounted in said box, a switch blade pivotally mounted in said box and movable by said blade actuator between an open position in which it is electrically disconnected from said stationary contact member and a closed POSition in which it is electrical- 1y connected to said stationary contact memberpa pin pivotably mounted in said second side wall, an operating handle pivotally mounted on said pin for movement between OFF and ON positions corresponding respectively to said open and closed positions of said switch blade, a releasable latch member mounted on said second side wall and disposed on the side of said handle closer to said first side wall, said latch member projecting forwardly beyond a front surface of said cover when said cover is in closed position and having a latching portion normally overlapping said front surface of said cover to latch said cover in closed position, the outer end portion of said latch member being movable in a direction away from said first side wall when said handle is in said OFF position and said switch blade is in said open position to move said latching portion out of latching relationship with said cover, an operating cam disposed on the side of said latch member closer to said first side wall and fixedly mounted on said pin for pivotal movement therewith, first lost motion connection means operatively connecting said handle and cam, second lost motion connection means operatively connecting said cam and blade actuator, a pair of spaced stop means respectively engageable by said cam and respectively limiting pivotal movement thereof in opposite direction, an over-center cam-biasing spring, and means operatively connecting said cam-biasing spring and said cam, said cam-biasing spring selectively biasing said cam in opposite directions into engagement respectively with said stop means, said cam and latch member having portions which interlock and prevent movement of said outer end portion of said' latch member in a direction away from said first side wall and movement of said latching portion out of latching relationship with said cover when said switch blade is in said closed position and said handle is in said ON position and said cam is biased into engagement with the corresponding one of said stop means by said cam-biasing spring, and said pin being pivotable against the force of said cam-biasing spring to turn said cam out of interlocking relationship with said latch member to a predetermined position between said stop means without shifting the line of action of said cam-biasing spring over the pivotal axis of said cam and pin, thereby to permit said outer end portion of said latch member to be moved in a direction away from said first side wall and said latching portion to be moved out of latching relationship with said cover and said cover to be opened while said switch blade is in said closed position and said handle is in said ON position.

6. A safety switch as claimed in claim 5, wherein when said handle is in said ON position and said switch blade is in said closed position, said handle may be moved to a predetermined intermediate position to move said cam to said predetermined position thereof between said stop means and out of interlocking relationship with said latch member without shifting the line of action of said cambiasing spring over the pivotal axis of said cam and pin, said handle when in said intermediate position having a portion preventing movement of said outer end portion of said latch member in a direction away from said first side wall and movement of said latching portion out of latching relationship with said cover, whereby said latching portion may be moved out of latching relationship with said cover and said cover may be opened while said switch blade is in said closed position solely by prior pivotal movement of said pin independently of said handle to move said cam to said predetermined position thereof.

7. A safety switch as claimed in claim 5, wherein said latch member is loosely mounted on said pin and prevented from turning with said pin.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Carman 200-15 Aalborg 200-15 Millermaster et a1. 200-50 Quast 200-50 Harlow et a1 200-114 Harlow 200-114 Platz 200-50 Jones et a1. 200-50 Bodenshatz et a1 200-50 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. A SAFETY SWITCH COMPRISING AN OPEN-FRONT BOX HAVING A REAR WALL AND A PAIR OF OPPOSED FIRST AND SECOND SIDE WALLS, AN OPENABLE COVER PIVOTALLY MOUNTED ON SAID FIRST SIDE WALL AND NORMALLY CLOSING THE OPEN FRONT OF SAID BOX, A STATIONARY CONTACT MEMBER MOUNTED IN SAID BOX, A BLADE ACTUATOR MOVABLY MOUNTED IN SAID BOX, A SWITCH BLADE MOUNTED IN SAID BOX AND MOVABLE BY SAID BLADE ACTUATOR BETWEEN AN OPEN POSITION IN WHICH IT IS ELECTRICALLY DISCONNECTED FROM SAID STATIONARY CONTACT MEMBER AND A CLOSED POSITION IN WHICH IT IS ELECTRICALLY CONNECTED TO SAID STATIONARY CONTACT MEMBER, AN OPERATING HANDLE PIVOTALLY MOUNTED ON SAID SECOND SIDE WALL FOR MOVEMENT BETWEEN OFF AND ON POSITIONS CORRESPONDING RESPECTIVELY TO SAID OPEN AND CLOSED POSITIONS OF SAID SWITCH BLADE, A RELEASABLE LATCH MEMBER MOUNTED ON SAID SECOND SIDE WALL AND DISPOSED BETWEEN SAID HANDLE AND SAID FIRST SIDE WALL, SAID LATCH MEMBER PROJECTING FORWARDLY BEYOND A FRONT SURFACE OF SAID COVER WHEN SAID COVER IS IN CLOSED POSITION AND HAVING A LATCHING PORTION NORMALLY OVERLAPPING SAID FRONT SURFACE OF SAID COVER TO LATCH SAID COVER IN CLOSED POSITION, THE OUTER END PORTION OF SAID LATCH MEMBER BEING MOVABLE IN A DIRECTION AWAY FROM SAID FIRST SIDE WALL WHEN SAID HANDLE IS IN SAID OFF POSITION AND SAID SWITCH BLADE IS IN SAID OPEN POSITION TO MOVE SAID LATCHING PORTION OUT OF LATCHING RELATIONSHIP WITH SAID COVER, AN OPERATING CAM PIVOTALLY MOUNTED ON SAID SECOND SIDE WALL, FIRST LOST MOTION CONNECTED MEANS OPERATIVELY CONNECTING SAID HANDLE AND CAM, SECOND LOST MOTION CONNECTION MEANS OPERATIVELY CONNECTING SAID CAM AND BLADE ACTUATOR, A PAIR OF SPACED STOP MEANS IN SAID BOX RESPECTIVELY ENGAGEABLE BY SAID CAM AND RESPECTIVELY LIMITING PIVOTAL MOVEMENT THEREOF IN OPPOSITE DIRECTIONS, AN OVER-CENTER CAM-BIASING SPRING, AND MEANS OPERATIVELY CONNECTING SAID CAM-BIASING SPRING AND SAID CAM, SAID CAM-BIASING SPRING SELECTIVELY BIASING SAID CAM IN OPPOSITE DIRECTIONS INTO ENGAGEMENT RESPECTIVELY WITH SAID STOP MEANS, SAID CAM AND LATCH MEMBER HAVING PORTIONS WHICH INTERLOCK AND PREVENT MOVEMENT OF SAID OUTER END PORTION OF SAID LATCH MEMBER IN A DIRECTION AWAY FROM SAID FIRST SIDE WALL AND MOVEMENT OF SAID LATCHING PORTION OUT OF LATCHING RELATIONSHIP WITH SAID COVER WHEN SAID SWITCH BLADE IS IN SAID CLOSED POSITION AND SAID HANDLE IS IN SAID ON POSITION AND SAID CAM IS BIASED INTO ENGAGEMENT WITH THE CORRESPONDING ONE OF SAID STOP MEANS BY SAID CAM-BIASING SPRING, AND SAID CAM BEING PIVOTABLE AGAINST THE FORCE OF SAID SPRING OUT OF INTERLOCKING RELATIONSHIP WITH SAID LATCH MEMBER TO A PREDETERMINED POSITION BETWEEN SAID STOP MEANS WITHOUT SHIFTING THE LINE OF ACTION OF SAID CAM-BIASING SPRING OVER THE PIVOTAL AXIS OF SAID CAM, THEREBY TO PERMIT SAID OUTER END PORTION OF SAID LATCH MEMBER TO BE MOVED IN A DIRECTION AWAY FROM SAID FIRST SIDE WALL AND SAID LATCHING PORTION TO BE MOVED OUT OF LATCHING RELATIONSHIP WITH SAID COVER AND SAID COVER TO BE OPENED WHILE SAID SWITCH BLADE IS IN SAID CLOSED POSITION AND SAID HANDLE IS IN SAID ON POSITION. 